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Thread: green screen chroma key causes transparency where not wanted.

  1. #1

    Default green screen chroma key causes transparency where not wanted.

    I am trying to use chroma key for a green screen effect, but every time I do it, the top layer video becomes transparent where not wanted. Is there anyway of solving this problem?

  2. #2

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    Here are screenshots of before and after. I'm using Sony Vegas movie studio platinum 6.0
    shotbefore.jpgshotafter.jpg
    Last edited by pickles4uk; 08-04-2012 at 11:06 PM.

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    The issue is not the software it's the shooting. The car roof is clearly green as is much of the rest of the scene (man's jackket etc). You need to key out a massive variety of shades of green with all those folds in the green screen and some of those shades match the green shdes of the ceiling. You really need to shoot tis again. Make the green in the background as evenly lit as possible (and get rid of all folds/creases). Light the inside of the car separately to stop the green from the screen reflecting onto it.
    Tim

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    FWIW I understand pros introduce a little red into the scene (in this case car interior) . . . so as to dispell any green casts.
    Whilst I can't see from the thumbnails, the green screen should be as far away as possible. Stronger lighting in the car can be altered by manipulating the Interior/exterior footage brightness, as the interior should be darker by day - and - brighter by night...
    All IMHO

    Hope that helps.

  5. #5

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    I'm placing the green screen footage on one track and the background footage below. Then I'm clicking on fx on the green screen footage and selecting chroma key and using the pipette to select the green i want to remove.

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    Quote Originally Posted by pickles4uk View Post
    I'm placing the green screen footage on one track and the background footage below. Then I'm clicking on fx on the green screen footage and selecting chroma key and using the pipette to select the green i want to remove.
    In Vegas you need to fiddle with the low threshold, the high threshold and blur amount.
    Take the blur amount right down. Fiddle with the others, then increase blur to get rid of alieasing on the edges.
    I found a low threshold of 0.495, a high threshold of 0.442 and a blur amount of 0.063 produced adequate results.

    Also switch the "show mask only" on occasionally - this gives a very clear idea of what is being keyed out.
    Tim

  7. #7

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    You've got to the very edge of what you can do, without needing to do a reshoot - which I would! Wrinkles and careful lighting are the only way. You've really got to the very edge.

    In the previous Chroma the guy's wrist has got thin and his nose is shaved!

    However, this is my feeble attempt in Vegas.

    chroma 5 August.JPG


    ........

  8. #8

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    Yup!

    . . . .

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